Alaska scientist uses isotopes to trace marijuana

May 9, 2007

By Ned RozellFairbanks, Alaska - Police officers don't often get a straight story when they ask a driver
where he got that bag of marijuana under his car seat. In the near future, they might be able to ask the marijuana itself.

Marijuana grown in the Goldstream Valley north of Fairbanks. Police officers found more than 400 plants at the scene a few years ago. Photo
courtesy UAF Police Department Investigator Steve Goetz.

Using a process called stable-isotope analysis, Alaska scientists have
been working with law enforcement officials to trace marijuana to the area in which it grew.

Matthew Wooller is one of those scientists. He runs the Alaska Stable
Isotope Facility at the University of Alaska Fairbanks, where
researchers
break substances down to their chemical elements to learn where they
came
from. Wooller went to a conference in New Zealand a few years ago where
a
scientist lectured about using stable isotopes to track people and
counterfeit money, to sniff out the source of explosions, and to find
the
sources of illegal drugs. The talk inspired him.

"When I was flying back to Alaska, I thought, I'd love to do an Alaska
forensic drug study," he said.

Marijuana is the most abused and widespread drug in Alaska, according
to the
U.S. Drug Enforcement Administration. Alaska features potent strains
from
the Matanuska Valley that make the state an exporter as well as an
importer.
Law enforcers would like to know the proportions of both, so they know
where
to focus their energy.

After Wooller applied for a permit from the D.E.A. to work with
marijuana in
his lab, he needed to find a varied supply of the drug. He went to the
UAF
Police Department and asked for help. After convincing a few officers
that
no, he was really a scientist, he got to speak with Investigator Steve
Goetz
and Lieutenant Syrilyn Tong, who agreed to help him out.

The UAF Police Department, with help from federal, state, and local law
enforcement agencies in Alaska, was able to provide Wooller's team with
marijuana samples from different areas in Alaska. They also gave
Wooller and
his research team of Norma Haubenstock and Tim Howe samples that
officers
had confiscated on and around the Fairbanks campus.

Wooller and his group then went to work, taking pinhead-size bits of
marijuana and vaporizing them, then running the gas samples through a
stable
isotope ratio mass spectrometer. That device allows them to measure the
composition of chemical elements such as oxygen, hydrogen, carbon, and
nitrogen in each sample. Stable isotopes are atoms of the same element
that
have slight differences in their atomic masses, and that's what enables
scientists to track things down with them.

For example, the stable oxygen isotope signature of well water in
Anchorage
is lower than that of tap water in Albany, New York. Leaves, buds, and
stems
of marijuana retain an isotopic signature of the water supplied to them
when
they were growing, and that allows researchers to tease out the
latitude at
which the marijuana grew.

"Marijuana grown in Alaska using Alaska water should have a distinct
chemical composition, completely different than marijuana grown in
Mexico,"
Wooller said. "And even Juneau and Fairbanks have very different
tap-water
signatures."

In his studies, Wooller found marijuana with both high and low isotopic
values, which suggests that some was imported from outside Alaska and
some
was grown in the state.

"The interesting thing we found is that there's a lot of marijuana
being
imported," said Goetz, the UAF investigator. "We had thought that a lot
higher percentage of marijuana in our area was locally grown."

Wooller, who studies the isotopic signatures of fossil plants and
animals
most of the time, is looking for more funding to continue the marijuana
study, which is on hold at the moment. Goetz hopes new money comes
through,
because law enforcers would like another tool to help trace marijuana
to its
source.

"Wešre still collecting samples for him," Goetz said. "I'm hoping he
continues with his project and gets more definitive answers for us."

This column is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Ned Rozell is a science writer at the institute.